Oligosaccharides occurring naturally in glycolipids, glycoproteins and proteoglycans have been ascribed a variety of functions in biological systems (see Varki, A. Glycobiology 3, 97(1993)). Although the universality of these functions is unknown at this point in time, there are properties of oligosaccharides which make them of immediate practical importance because of their possible use as human therapeutics and, particularly important, as preventive agents of human infections. For prevention purposes, these polyvalent carbohydrate molecules can be used as food additives, dental cleansers, mouthwashes, eardrops, ointments, and similar agents. Infections caused by colonization mediated by adherence to tissues through carbohydrate substrate binding are targets of these preventive agents.
As an example, such adherence is the adhesion of pathogens to human epithelia through the binding of pathogens to epithelial cells by bacterial or parasital adhesins. Adhesins are proteins showing specific binding affinity to oligosaccharide (carbohydrate) moieties of glycolipids and glycoproteins displayed on epithelial cells in colonized tissues. Since the attachment to host cells is the initial event of the infectious process, interference with binding by oligosaccharides mimicking the oligosaccharide moieties of glycolipids or glycoproteins prevents (see Zopf, D., Roth, S. Lancet 347, 1017 (1996)) or reduces the infection. Such attachment also occurs when the carbohydrate is located on the pathogen and therefore the binding to the host's proteins is mediated by this carbohydrate. Thus carbohydrates naturally occurring in human milk (see Anianson, G., Andersson, B., Lindstedt, R. & Svanborg, C., Microbial Pathogenesis 8, 315) offer protection to infants against infections. Carbohydrates may, in addition to protection against infection, be utilized for treatment of infectious diseases that are increasingly more difficult to treat because of growing pathogen resistance to antibiotics and drugs.
Since individual natural oligosaccharides usually bind to their accepting molecules weakly, individual oligosaccharides must be used in impracticably large quantities for an effective treatment. This problem is overcome in carbohydrate polyvalent molecules [see Zopf, D., Roth, S. Lancet 347, 1017 (1996)] since such molecules bind the accepting molecules through multiple contacts resulting in strong binding. These polyvalent molecules occupy the carbohydrate binding site tightly and the infectious process is thus interrupted. The combinatorial polyvalent oligosaccharide molecule has a further advantage of making it possible to utilize the strongest binders and their combinations for a particular pathogenic bacterium without any prior knowledge of exact binding requirements of the particular microorganism. The matrix molecule should be a biocompatible material, not eliciting an immune response, suitable for the purpose, for instance a starch for infant foods or a gel-forming oligosaccharide such as a carrageenan for dental pastes, or a similar scaffold for disruption or removal of biofilms. However, all matrices can be considered for all applications. The biofilms are often responsible for infective properties of microorganisms, for failures of implanted bioengineering devices, as well as for malfunctions of engineering structures such as oil pipelines, and the water intakes of municipal water and industrial plants.